This invention relates to shadowmask supporting studs for cathode ray tubes.
Face panels for some cathode ray tubes, particularly those used to display images in color, include a frontal portion having a peripheral wall upstanding therefrom. The frontal or viewing portion generally comprises a spherical, cylindrical or flat section, defining a generally flat plane. The upstanding wall of such face panels has a plurality of studs retained therein for supporting a shadow mask or color-selecting electrode. These tubes generally employ three or four studs spaced 120xc2x0 to 90xc2x0 apart, respectively. Studs, which have been frequently employed in the past, are shown in U.S. Pat. Nos. 3,379,913, and 4,755,713.
Newer styles of CRT""s, such as those now used for color television or computer monitors, have more nearly square corners than older types and have employed different types of studs. Primary among these newer types are those using a base member for embedment into the glass wall of the tube together with a spherical projection for engaging a spring member mounted upon the shadow mask. Such studs are shown, for example, in U.S. Pat. Nos. 4,644,222; 4,987,337; 4,868,453; 4,763,039; and 4,730,142, and utilize bases that can be solid or hollow and cup-shaped. The spherical projection can be formed in the material or, as more likely, welded to a previously formed stud. In the former technique shaping the ball end adds considerable cost. The latter technique requires forming the face of the stud to a configuration matching that of the sphere to be attached, usually by cold-working the material without fracturing it or, in the case of a solid base, accurately positioning and holding the sphere while welding or other suitable attachment takes place. See in particular U.S. Pat. No. 4,868,453. While all of these various studs have been used with some success, problems have existed, not only with regard to cost, but also by causing interference with non-destructive-testing procedures (NDT), such as eddy-current testing which can be difficult if the weld bead holding the sphere to the body is less than 360xc2x0.
It is, therefore, an object of the invention to obviate the disadvantages of the prior art.
It is another object of the invention to enhance CRT studs.
These objects are accomplished, in one aspect of the invention, by the provision of a CRT stud for mounting a shadowmask which stud comprises a tubular body symmetrically arrayed about a longitudinal axis. The body has a first end having a first diameter formed to engage a wall of the cathode ray tube and has a second end formed to receive a sphere. The sphere has a diameter larger than that of the body. In a preferred embodiment the stud comprises a tubular body symmetrically arrayed about a longitudinal axis. The body has a first portion formed to engage a wall of the cathode ray tube and a first diameter and a second portion extending therefrom, the second portion having a second diameter smaller than said first diameter. As used herein the term tubular refers to a more or less cylindrical, hollow construction that is open at both ends. By making the stud tubular, the step of forming the face of the stud to match the diameter of the sphere is eliminated. The cost is reduced and welding becomes easier, as does NDT.